Electronic pen central rod and electronic pen main body part

ABSTRACT

An electronic pen central rod is provided. The electronic pen central rod includes a connection member having a front end and a back end, and a front-end member having a pen tip part and a back-end extension part that extends in an opposite direction from the pen tip part to be detachably held by the front end of the connection member with a first level of holding strength. The electronic pen central rod further includes a back-end member having an attachment part to be attached to an electronic pen interior and a front-end extension part that extends in an opposite direction from the attachment part to be held by the back end of the connection member with a second level of holding strength. The second level of holding strength is higher than the first level of holding strength.

BACKGROUND Technical Field

The present disclosure relates to an electronic pen central rod and anelectronic pen main body part configured by use of the electronic pencentral rod.

Description of the Related Art

Some electronic devices such as smartphones and personal computers (PC)include a position detection device formed of a position detectionsensor and a position detection circuit. Such electronic devices arewidely used with an electronic pen functioning as an operating elementthat permits pointing input to the electronic device. Such electronicdevices are made increasingly smaller and thinner in size and thickness,and so is the electronic pen that is made smaller and thinner. In orderto make the electronic pen smaller and thinner, it is necessary to alsomake an electronic pen central rod smaller and thinner, which tends toreduce the strength of the electronic pen central rod.

WO 2016/185915 (Patent Document 1 hereunder) discloses an electronic pencentral rod configured with a metal pipe part, to one end of which aresin pen tip part is press-inserted and secured, and to the other endof which a writing pressure transmission part made of resin ispress-inserted and secured. WO 2020/235342 (Patent Document 2 hereunder)discloses an electronic pen central rod configured with a metal axialcenter forming part (pipe part), to one end of which a felt pen tip partis inserted and fitted, and to the other end of which a fitting partmade of hard resin is inserted and fitted.

Each of the disclosed electronic pen central rods includes the metalpipe part to form a high-strength, hard-to-break electronic pen centralrod. In the case of the electronic pen central rod disclosed in PatentDocument 2, it is explained that the method of coupling the metal axialcenter forming part (pipe part) with the pen tip part and with thefitting part entails use of adhesives. It is also explained that, in acase where the axial center forming part is made of hard resin, fusionbonding is used.

In the case of the electronic pen central rod disclosed in PatentDocument 1, both the pen tip part and the writing pressure transmissionpart are press-inserted into the pipe part, and the strength of theconnection between these components is not high. There is a possibilitythat, when the pen tip part is strongly pressed, for example, against anoperation surface to be used, the pen tip part may be detached ordislodged. On the other hand, in the case of the electronic pen centralrod disclosed in Patent Document 2, because the pen tip part and thefitting part are bonded by adhesive to the pipe part, it is difficult toremove the pen tip part from the pipe part to replace only the pen tippart. Also, the manufacturing process of the electronic pen central rodtends to be time consuming.

In order to make the electronic pen central rod smaller and thinner asdescribed above, it is preferable that the overall strength of thecentral rod be ensured while the manufacturing process of the centralrod is made as simple as possible. Furthermore, the usability of theelectronic pen central rod is desired to be improved by making the pentip part (front-end forming part) easily replaceable or by reducing thephysical load applied to a portion at which the central rod is attachedto the electronic pen. That is, in the case of the electronic pen thatpermits detection of writing pressure, the electronic pen central rod isconfigured to apply pressure to a writing pressure detection part, andif the writing pressure detection part and the electronic pen centralrod are frequently connected to or disconnected from each other, theconnecting portion therebetween can be worn out or deformed so as toaffect the detection of writing pressure.

BRIEF SUMMARY

The present disclosure has been made in view of the above circumstances.An aspect of the disclosure is directed to providing an electronic pencentral rod which has high strength, withstands rough use, permits easyreplacement of a pen tip part, and has a high affinity with anelectronic pen to which the central rod is attached.

In solving the above problem and according to one embodiment of thepresent disclosure, there is provided an electronic pen central rodincluding a front-end member configured as a rod-like body having a pentip part and a back-end extension part that extends from a back-end faceof the pen tip part in an opposite direction of the pen tip part, aback-end member configured as a rod-like body having an attachment partto be detachably attached to an electronic pen interior and a front-endextension part that extends from a front-end face of the attachment partin an opposite direction of the attachment part, and a connection memberconfigured as a rod-like body having two end sides, one of the two endsides being provided with a front-end hole part into which the back-endextension part of the front-end member is inserted, the other end sidebeing provided with a back-end hole part into which the front-endextension part of the back-end member is inserted. An engagement portionbetween the back-end extension part of the front-end member and theconnection member is provided with a front-end holding part thatdetachably holds the inserted back-end extension part of the front-endmember with a predetermined level of holding strength, and an engagementportion between the front-end extension part of the back-end member andthe connection member is provided with a back-end holding part thatholds the inserted front-end extension part of the back-end member witha predetermined level of holding strength. The predetermined level ofholding strength between the back-end hole part and the front-endextension part is made higher than the predetermined level of holdingstrength between the front-end hole part and the back-end extensionpart.

In the electronic pen central rod outlined above, the engagement portionbetween the back-end extension part of the front-end member and theconnection member is provided with the front-end holding part thatdetachably holds the back-end extension part of the front-end member,which is inserted through the front-end hole part into the connectionmember, with the predetermined level of holding strength. The engagementportion between the front-end extension part of the back-end member andthe connection member is provided with the back-end holding part thatholds the front-end extension part of the back-end member, which isinserted through the back-end hole part into the connection member, withthe predetermined level of holding strength. The holding strengthbetween the back-end hole part and the front-end extension part is madehigher than the holding strength between the front-end hole part and theback-end extension part.

Consequently, both the front-end member and the back-end member can beattached to and held by the connection member with the predeterminedlevels of holding strength. This provides a high-strength electronic pencentral rod that is robust, that permits easy replacement of thefront-end member, and that can properly be attached to and detached froman electronic pen via the back-end member.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1A to 1C are views each explaining a configuration example of anelectronic pen according to the present disclosure;

FIGS. 2A and 2B are enlarged views each explaining a configurationexample of an electronic pen main body part having an electronic pencentral rod according to the present disclosure;

FIGS. 3A to 3F are views each explaining a configuration example of theelectronic pen central rod according to the present disclosure;

FIGS. 4A to 4F are views each explaining another configuration exampleof the electronic pen central rod according to the present disclosure;

FIG. 5 is a view explaining a further configuration example of theelectronic pen central rod according to the present disclosure;

FIGS. 6A to 6C are views each explaining an even further configurationexample of the electronic pen central rod according to the presentdisclosure;

FIG. 7 is a view explaining a still further configuration example of theelectronic pen central rod according to the present disclosure; and

FIG. 8 is a view explaining another configuration example of aconnection member of the electronic pen central rod according to thepresent disclosure.

DETAILED DESCRIPTION

Described below with reference to the accompanying drawings areembodiments of an electronic pen central rod according to the presentdisclosure along with embodiments of an electronic pen according to thisdisclosure. The electronic pen embodying the invention and explainedhereunder constitutes an exemplary electronic pen that supports positionpointing based on coupling with a position detection device viaelectromagnetic induction.

Configuration Example of the Electronic Pen 1

FIGS. 1A to 1C are views each depicting a configuration example of anelectronic pen used in conjunction with an electronic pen central rod.An electronic pen 1 of this embodiment houses an electronic pen mainbody part 3 inside a hollow part 2 a of a cylindrical housing 2. Theelectronic pen 1 has a knock cam mechanical part 4 with a knockmechanism by which the pen tip side of the electronic pen main body part3 is extended and retracted through an opening 2 b at one end of thehousing 2 in the longitudinal direction. In this embodiment, theelectronic pen main body part 3 has a configuration of a cartridge type,which allows for its attachment to and detachment from the housing 2.The electronic pen main body part 3 includes an electronic pen centralrod (simply referred to as the central rod hereunder) 7 embodying thepresent disclosure. The central rod 7 can be attached to and detachedfrom the electronic pen main body part 3. In the example of FIGS. 1A and1B, the housing 2 of the electronic pen 1 is formed with a transparentsynthetic resin, so that the inside of the housing 2 is visible.

The electronic pen 1 of this embodiment is configured to beinterchangeable with a commercially available knock type ballpoint pen.The housing 2 and the knock cam mechanical part 4 disposed therein havesubstantially the same configurations and dimensions as those of theircounterparts of a well-known commercially available knock type ballpointpen. As depicted in FIGS. 1A and 1B, the knock cam mechanical part 4 hasa well-known configuration that includes a cam body 41, a knocking rod42, and a rotator 43 in combination.

In the state of FIG. 1A, pressing an end part 42 a of the knocking rod42 causes the knock cam mechanical part 4 to lock the electronic penmain body part 3 into the state of FIG. 1B inside the housing 2. In thisstate, the pen tip side of the electronic pen main body part 3 projectsfrom the opening 2 b of the housing 2. In the state of FIG. 1B, againpressing the end part 42 a of the knocking rod 42 causes the knock cammechanical part 4 to unlock the electronic pen main body part 3. Areturn spring 5 brings the electronic pen main body part 3 back to itsposition in the housing 2 in the state of FIG. 1A. The detailedconfigurations and operations of the knock cam mechanical part 4 arewell known and will not be discussed further.

Configuration Example of the Electronic Pen Main Body Part 3

FIG. 1C is a view depicting a configuration example of the electronicpen main body part 3. FIGS. 2A and 2B are partially enlarged viewsexplaining how the pen tip side of the electronic pen main body part 3is configured. In the electronic pen main body part 3 of thisembodiment, as depicted in FIG. 1C, a magnetic material core, which is aferrite core 32 in this example and about which a coil 31 is wound, iscoupled with a cylindrical part 33. The central rod 7 is inserted into athrough-hole (not depicted in FIG. 1C) of the ferrite core 32 andattached detachably to a writing pressure detection part 6 (not depictedin FIGS. 1A to 1C; see FIGS. 2A and 2B) disposed in the cylindrical part33, thereby forming a portion of the electronic pen main body part 3. Asdepicted in FIGS. 1C and 2B, the central rod 7 has the end part of thepen tip side projected from the ferrite core 32.

As depicted in FIG. 2A, the ferrite core 32 of this example is made of,for example, a cylindrical ferrite material which has a through-hole 32a formed in the axial direction thereof, the through-hole 32 a having apredetermined diameter r1 (e.g., r1=1 mm) and allowing the central rod 7to be inserted. The ferrite core 32 has a tapered part 32 b formed onthe pen tip side, the tapered part 32 b gradually being tapered towardthe pen tip side. The tapered part 32 b is configured to providestronger magnetic coupling with a sensor of the position detectiondevice than if there is no tapered part 32 b. The central rod 7 is madeup of a front-end member 71, a connection member 72, and a back-endmember 73, as will be discussed later in detail.

In this embodiment, as depicted in FIG. 2A, the winding position of thecoil 31 over the ferrite core 32 is located disproportionately towardthe opposite side of the pen tip side and covers approximately half thetotal length of the ferrite core 32. A portion ranging from the end partof the ferrite core 32 on the pen tip side to one end of the coil woundpart constitutes a coil unwound part with no coil wound thereon.

Near the portion of the cylindrical part 33 that couples with theferrite core 32, the writing pressure detection part 6 is provided. Inthis example, the writing pressure detection part 6 is configured by useof a semiconductor element that varies in capacitance according towriting pressure, as disclosed in JP 2013-161307 A. Alternatively, thewriting pressure detection part 6 can also be configured with a variablecapacitance capacitor whose capacitance varies according to writingpressure by use of writing pressure detecting section with a knownmechanical configuration disclosed in JP 2011-186803 A.

The writing pressure detection part 6 is configured to be pressed by apressure transmission member 36 fitted with the back-end member 73 ofthe central rod 7. The pressure transmission member 36 has a fittingrecessed part 36 a. Fitting the back-end member 73 of the central rod 7into the fitting recessed part 36 a attaches the central rod 7 to thepressure transmission member 36. The pressure transmission member 36 isdisposed in a manner not to be detached or dislodged from the inside theelectronic pen main body part 3, but the pressure transmission member 36may be pushed in and returned slidably by a predetermined distance inthe longitudinal direction of the pressure transmission member 36according to the writing pressure applied to the central rod 7. In thismanner, the central rod 7 is detachably attached to the electronic penmain body part 3 via the pressure transmission member 36, and thewriting pressure applied to the central rod 7 can be transmitted to thewriting pressure detection part 6.

The cylindrical part 33 further houses a printed-circuit board 34. Theprinted-circuit board 34 carries a capacitor 35 connected in parallelwith the coil 31 to form a resonance circuit. The variable capacitancecapacitor constituted by the writing pressure detection part 6 isconnected in parallel with the capacitor 35 on the printed-circuit board34 to form part of the above-mentioned resonance circuit.

The electronic pen 1 of this embodiment is connected by electromagneticinduction with a loop coil of a position detection sensor of theposition detection device by means of the resonance circuit. Theelectronic pen 1 exchanges signals interactively with the loop coil. Theposition detection device detects the position pointed to by theelectronic pen 1 by detecting the position of the signal received on theposition detection sensor from the electronic pen 1. Also, the positiondetection device detects the writing pressure applied to the electronicpen 1 by detecting changes in frequency or phase of the signal receivedfrom the electronic pen 1.

As depicted in FIG. 2B, the coil unwound part of the ferrite core 32 onthe opposite side of the pen tip side is fitted into a recessed part 33a of the cylindrical part 33. The ferrite core 32 accordingly is coupledwith the cylindrical part 33. Although not illustrated, when the ferritecore 32 is coupled with the cylindrical part 33, two ends 31 a and 31 bof the coil 31 are electrically connected in parallel with the capacitor35 disposed on the printed-circuit board 34 in the cylindrical part 33.

First Configuration Example of the Electronic Pen Central Rod 7

FIGS. 3A to 3F are views each explaining a configuration example of thecentral rod 7 attached to the electronic pen main body part 3. Asdepicted in the external view of FIG. 3A, the central rod 7 isconfigured with the front-end member 71, connection member 72, and theback-end member 73. The front-end member 71 and the back-end member 73are each made of resin, synthetic rubber, or natural rubber, forexample. In this embodiment, these components are made of polyacetalresin (generally called POM). The front-end member 71 can be formed witha textile material such as a felt (non-woven fabric) so as to soften thewriting feel. The connection member 72 is made of a high-hardnessmaterial such as metal or hard resin to increase the strength of thecentral rod 7. In this embodiment, the connection member 72 is made ofstainless steel (generally called SUS).

As depicted in FIG. 3B, the connection member 72 is a hollow(through-hole) cylindrical (pipe-like) member with an inner diameter ofR1 and an outer diameter of R2. The through-hole 32 a of the ferritecore 32 through which the central rod 7 is inserted as explained abovewith reference to FIG. 2A has a diameter r1 of 1 mm, for example. Itfollows that the outer diameter R2 is 1 mm or less to permit insertioninto the through-hole 32 a. In the case of this example, a portion ofthe connection member 72 toward the side of the front-end member 71(left end side in FIG. 3B) forms a front-end hole part FH to which thefront-end member 71 is fitted; a portion of the connection member 72toward the side of the back-end member 73 (right side in FIG. 3B)constitutes a back-end hole part BH to which the back-end member 73 isfitted.

Furthermore, the connection member 72 has ring-shaped recessed parts 721a and 721 b which are pressed down along the outer circumference towardthe side of the front-end member 71 (left end side in FIG. 3B).Consequently, ring-shaped protruding parts 721 c and 721 d are formed toprotrude internally from those positions on the inner wall surface(inner side surface) which correspond to the ring-shaped recessed parts721 a and 721 b of the connection member 72. These ring-shapedprotruding parts 721 c and 721 d function as a front-end holding part.

Through-holes 722 a and 722 b are formed in a direction intersectingwith an axial center direction on the side surface (side wall) of theconnection member 72 toward the side of the back-end member 73 (rightside in FIG. 3B). Further, although not depicted in FIGS. 3A and 3B,through-holes 722 c and 722 d are formed in a direction intersectingwith the axial center direction on the side surface (side wall) of theconnection member 72 at the positions opposite from the through-holes722 a and 722 b across a hollow space inside. That is, on the sidesurface of the connection member 72, the through-hole 722 c is formed ina position opposite to the through-hole 722 a across the internal hollowspace, and the through-hole 722 d is disposed in a position opposite tothe through-hole 722 b across the internal hollow space. There are thusformed four through-holes 722 a, 722 b, 722 c, and 722 d. These fourthrough-holes 722 a, 722 b, 722 c, and 722 d, together with protrudingparts formed on the back-end member 73 to be discussed later, functionas a back-end holding part.

As depicted in FIG. 3C, the front-end member 71 is a rod-like body thatincludes a pen tip part 711 with its appearance shaped like a dome, andincludes a back-end extension part 712 extending from a back-end face711 a of the pen tip part 711 in an opposite direction from the pen tippart 711. The back-end face 711 a of the pen tip part 711 has a diameterslightly larger than the outer diameter R2 of the connection member 72.In this embodiment, the back-end extension part 712 of the front-endmember 71 has a cylindrical shape with the diameter R1.

As depicted in the cross-sectional view of the central rod 7 in FIG. 3E,the front-end member 71 shaped as described above is press-inserted intothe front-end hole part FH of the connection member 72, from theback-end side of the back-end extension part 712 through the opening onthe left end side of the connection member 72. In this manner, thefront-end member 71 is attached to the connection member 72. In thiscase, the back-end face of the pen tip part 711 of the front-end member71 is butted against the front-end face (left end face) of theconnection member 72. This prevents the front-end member 71 from furtherentering into the connection member 72. Furthermore, the ring-shapedprotruding parts 721 c and 721 d formed on the inner wall surface of theconnection member 72 function as a front-end holding part. This bringsabout a state in which the side surface of the back-end extension part712 of the front-end member 71 is held down. The front-end member 71 canthus be attached to the connection member 72 with a constant level ofholding strength. The back-end extension part 712 can have a diameterclose to the length R1 as long as the back-end extension part 712 can beinserted through the opening on the left end side of the connectionmember 72. However, it is not desirable to make the diameter of theback-end extension part 712 unnecessarily smaller than the length R1because this causes the back-end extension part 712 to be easilydetached or dislodged.

As depicted in FIG. 3D, the back-end member 73 is a rod-like body thatincludes an attachment part 731 to be detachably attached to theelectronic pen main body part 3, an engagement part 732, and a front-endextension part 733 extending from a front-end face 732 a of theengagement part 732 in an opposite direction from the attachment part731. The attachment part 731 and the front-end extension part 733 of theback-end member 73 are both cylindrically shaped and disposed on bothsides of the engagement part 732. The engagement part 732, shaped as acircular plate with a predetermined thickness, separates the attachmentpart 731 and the front-end extension part 733 from each other. Theattachment part 731 of the back-end member 73 has fitting protrusions731 a and 731 b as depicted in FIG. 3D.

Meanwhile, as depicted in FIG. 3D, the front-end extension part 733 hasprotruding parts 733 a and 733 b positioned opposite from protrudingparts 733 c and 733 d respectively, with a main body portion of thefront-end extension part 733 interposed therebetween. The protrudingparts 733 a and 733 b of the front-end extension part 733 are positionedcorresponding to the through-holes 722 a and 722 b of the connectionmember 72, respectively. The protruding parts 733 c and 733 d arepositioned corresponding to the through-holes 722 c and 722 d of theconnection member 72, respectively. The main body portion of thefront-end extension part 733 has the diameter R1 as depicted in FIG. 3D.

As depicted in the cross-sectional view of the central rod 7 in FIG. 3E,the back-end member 73 is inserted into the back-end hole part BH of theconnection member 72 through the opening on the right end side of theconnection member 72 from the front-end side of the front-end extensionpart 733. In this manner, the back-end member 73 is attached to theconnection member 72. In this case, the members are aligned in such amanner that the protruding parts 733 a and 733 b of the front-endextension part 733 are fitted into the through-holes 722 a and 722 b ofthe connection member 72, respectively, and that the protruding parts733 c and 733 d of the front-end extension part 733 are fitted into thethrough-holes 722 c and 722 d of the connection member 72, respectively.This is how the back-end member 73 is securely attached to theconnection member 72. With the front-end face of the engagement part 732butted against the back-end face of the connection member 72, theback-end member 73 is prevented from further entering into theconnection member 72.

For the purpose of simplification, the protruding parts 733 a through733 d are explained specifically to correspond to the through-holes 722a and 722 d, respectively. However, given that the protruding parts 733a and 733 b are located opposite from the protruding parts 733 c and 733d and that the through-holes 722 a and 722 b are also located oppositefrom the protruding parts 733 c and 733 d, it is possible to fit theprotruding parts 733 a through 733 b into the through-holes 722 c and722 d and the protruding parts 733 c and 733 d into the through-holes722 a and 722 b with the same effect in attaching the members.

Obviously, it is possible to detach the back-end member 73 from theconnection member 72. In this case, the back-end member 73 is axiallyrotated relative to the connection member 72 or forcibly extractedtherefrom in a manner to detach or dislodge the protruding parts 733 a,733 b, 733 c, and 733 d from the through-holes 722 a, 722 b, 722 c, and722 d of the connection member 72. The front-end extension part 733 canhave a diameter close to the length R1 as long as the front-endextension part 733 can be inserted through the opening on the right endside of the connection member 72. However, it is not desirable to makethe diameter of the front-end extension part 733 unnecessarily smallerthan the length R1 because this causes the front-end extension part 733to be easily detached or dislodged.

Meanwhile, as explained above with reference to FIGS. 2A and 2B, theattachment part 731 of the back-end member 73 is fitted into the fittingrecessed part 36 a of the pressure transmission member 36 inside theelectronic pen main body part 3. The fitting protrusions 731 a and 731 bcome into strong contact with the inner wall surface of the fittingrecessed part 36 a. That is, as depicted in the cross-sectional view ofthe back-end member 73 and the pressure transmission member 36 in FIG.3F, the attachment part 731 excluding the fitting protrusions 731 a and731 b has a length R3, which is the same as the diameter of the fittingrecessed part 36 a of the pressure transmission member 36.

Thus, the attachment part 731 of the back-end member 73 has its frontend press-inserted and fitted into the fitting recessed part 36 a of thepressure transmission member 36. In this case, the fitting protrusions731 a and 731 b come into strong contact with the inner wall surface ofthe fitting recessed part 36 a. The fitting protrusions 731 a and 731 band the inner wall surface of the fitting recessed part 36 a are engagedwith one another with a predetermined level of holding strength,allowing the central rod 7 to be attached to the pressure transmissionmember 36. With the central rod 7 thus attached to the pressuretransmission member 36, the writing pressure applied to the central rod7 pushes up the pressure transmission member 36. In turn, a pressingpart 36 b of the pressure transmission member 36 presses the writingpressure detection part 6. When the writing pressure to the central rod7 is released, the pressure transmission member 36 and the central rod 7are pushed back and return to their initial positions.

In this embodiment, the connecting portion between the connection member72 and the front-end extension part 733 of the back-end member 73 hasthe highest holding strength when the through-holes 722 a et al. and theprotruding parts 733 a et al. are fitted to one another. This ensureshard-to-detach connection between the connection member 72 and theback-end member 73. The connecting portion between the attachment part731 of the back-end member 73 and the pressure transmission member 36has the second-highest holding strength with a wide area of contactformed between the fitting protrusions 731 a and 731 b on one hand, andthe inner wall surface of the fitting recessed part 36 a of the pressuretransmission member 36 on the other hand. The connecting portion betweenthe connection member 72 and the back-end extension part 712 of thefront-end member 71 has the third-highest holding strength because of arelatively small portion of contact between the ring-shaped protrudingparts 721 c and 721 d on the inner wall surface of the connection member72 on one hand, and the back-end extension part 712 on the other hand.

There are three types of holding strength: the holding strength withwhich the connection member 72 holds the back-end extension part 712 ofthe front-end member 71; the holding strength with which the connectionmember 72 holds the front-end extension part 733 of the back-end member73; and the holding strength with which the pressure transmission member36 holds the attachment part 731 of the back-end member 73.Specifically, the holding strength means a strength high enough formembers to maintain their connected state by means of frictional forceof the connecting portion between the members, or by use of engagingforce of (force to engage with) through-holes or recesses andprojections formed over the connecting portion between the members.

For this embodiment, it is assumed that a value A stands for the holdingstrength of the connecting portion between the connection member 72 andthe front-end extension part 733 of the back-end member 73, that a valueB denotes the holding strength of the connecting portion between theattachment part 731 of the back-end member 73 and the pressuretransmission member 36, and that a value C represents the holdingstrength of the connecting portion between the connection member 72 andthe back-end extension part 712 of the front-end member 71. In a casewhere the central rod 7 depicted in FIGS. 3A to 3F is used, therelations between these types of holding strength are A>B>C. That is,the connecting portion between the connection member 72 and thefront-end extension part 733 of the back-end member 73 has the highestholding strength; the connecting portion between the attachment part 731of the back-end member 73 and the pressure transmission member 36 hasthe second-highest holding strength; and the connecting portion betweenthe connection member 72 and the back-end extension part 712 of thefront-end member 71 has the third-highest holding strength.

Thus, when the central rod 7 is thus attached to the electronic pen mainbody part 3, the central rod 7 can be pulled, by a user pinching the pentip part 711 of the front-end member 71 with nails, for example, andpulling the central rod 7 with a force that is lower than the holdingstrength B but greater than the holding strength C. In such case, whilethe attachment part 731 of the back-end member 73 of the central rod 7remains attached to the pressure transmission member 36, the front-endmember 71 can be extracted (separated) from the connection member 72.That is, with the central rod 7 attached to the electronic pen main bodypart 3, the front-end member 71 alone can be replaced. Because theback-end extension part 712 of the front-end member 71 is relativelylong, the front-end member 71 can be extracted from the connectionmember 72, for example, by repeatedly pulling the central rod 7, eachtime for a short period of time with a force that is greater than theholding strength C.

With the central rod 7 attached to the electronic pen main body part 3,the central rod 7 can be pulled, by a user holding the pen tip part 711of the front-end member 71 with nails, for example, and pulling thecentral rod 7 with a force that is lower than the holding strength A andhigher than the holding strength B. In this case, because the back-endextension part 712 of the front-end member 71 is long, the entirecentral rod 7 can be extracted from the electronic pen main body part 3before the front-end member 71 is extracted out of the connection member72. That is, the central rod 7 as a whole can be replaced, as needed.

As depicted in FIG. 3E, a void space 74 is provided between the back-endface of the back-end extension part 712 of the front-end member 71 andthe front-end face of the front-end extension part 733 of the back-endmember 73. However, the presence of the void space 74 is not alwaysrequired. Either of or both of the back-end extension part 712 of thefront-end member 71 and the front-end extension part 733 of the back-endmember 73 may be elongated to make the void space 74 as narrow aspossible, which will enhance the strength of the central rod 7.

Second Configuration Example of the Electronic Pen Central Rod 7

FIGS. 4A to 4F are views each explaining a central rod 7A as anotherconfiguration example of the central rod 7 to be attached to theelectronic pen main body part 3. Of the components of the central rod 7Ain FIGS. 4A to 4F, those configured substantially the same as theircounterparts of the central rod 7 in FIGS. 3A to 3F are designated bythe same reference signs. As depicted in the external view of FIG. 4A,the central rod 7A of this example is configured with a front-end member71, a connection member 72A, and a back-end member 73A. That is, themembers making up the central rod 7A are similar to the three types ofmembers in the case of the central rod 7 explained above with referenceto FIGS. 3A to 3F, except that the connection member 72A and theback-end member 73A are configured differently from the connectionmember 72 and the back-end member 73 of the central rod 7 in FIGS. 3A to3F. With the central rod 7A of the present example, the front-end member71, the connection member 72A, and the back-end member 73 are made ofthe same materials as those of the corresponding members of the centralrod 7 explained above with reference to FIGS. 3A to 3F.

With the central rod 7A of this example, as depicted in FIG. 4B, theconnection member 72A is also a pipe-like (cylindrical) member with ahollow interior. The connection member 72A has inner diameter R1 andouter diameter R2, which are the same as those of the connection member72 in FIG. 3B. In this example as well, a portion of the connectionmember 72A on the side toward the front-end member 71 (on the left endside in FIG. 4B) forms a front-end hole part FH to which the front-endmember 71 is fitted; and a portion of the connection member 72A towardthe side of the back-end member 73A (on the right end side in FIG. 4B)constitutes a back-end hole part BH to which the back-end member 73A isfitted.

Also, the connection member 72A in FIG. 4B has ring-shaped recessedparts 721 a and 721 b which are pressed down along the outercircumference toward the side of the front-end member 71 (on the leftend side in FIG. 4B). Consequently, ring-shaped protruding parts 721 cand 721 d are formed to protrude internally from those positions of theinner wall surface (inner side surface) which correspond to thering-shaped recessed parts 721 a and 721 b of the connection member 72A.These ring-shaped protruding parts 721 c and 721 d function as afront-end holding part.

Further, the connection member 72A of this example has ring-shapedrecessed parts 723 a and 723 b which are pressed down along the outercircumference toward the side of the back-end member 73A (right end sidein FIG. 4B). Consequently, ring-shaped protruding parts 723 c and 723 dare formed to protrude internally from those positions of the inner wallsurface (inner side surface) which correspond to the ring-shapedrecessed parts 723 a and 723 b of the connection member 72A. Thering-shaped protruding parts 723 c and 723 d function as a back-endholding part. As depicted in FIG. 4B, the ring-shaped recessed parts 723a and 723 b toward the side of the back-end member 73A are wider in thelongitudinal direction than the ring-shaped recessed parts 721 a and 721b on the side of the front-end member 71.

As depicted in FIG. 4C, the front-end member 71 is configured similarlyto the front-end member 71 explained above with reference to FIG. 3C andthus will not be discussed further in detail to avoid duplication. Asdepicted in the cross-sectional view of the central rod 7A in FIG. 4E,the front-end member 71 is press-inserted into the front-end hole partFH of the connection member 72A through the opening on the left end sideof the connection member 72A, from the back-end side of the back-endextension part 712. This allows the front-end member 71 to be attachedto the connection member 72A in a manner similar to that of the centralrod 7 explained above with reference to FIGS. 3A to 3F. That is, thering-shaped protruding parts 721 c and 721 d formed on the inner wallsurface of the connection member 72A function as a front-end holdingpart. This brings about a state in which the side surface of theback-end extension part 712 of the front-end member 71 is held down. Thefront-end member 71 can thus be attached to the connection member 72Awith a constant level of holding strength.

In this case, the back-end face of the pen tip part 711 of the front-endmember 71 and the front-end face (left end side) of the connectionmember 72A are butted against each other. This prevents the front-endmember 71 from further entering into the connection member 72. As in thecase of the central rod 7 in FIGS. 3A to 3F, the back-end extension part712 of the front-end member 71 can have a diameter close to the lengthR1 as long as the back-end extension part 712 can be inserted throughthe opening on the left end side of the connection member 72A. However,it is not desirable to make the diameter of the back-end extension part712 unnecessarily smaller than the length R1 because this may cause theback-end extension part 712 to be easily detached or dislodged.

As depicted in FIG. 4D, the back-end member 73A is a rod-like body thatincludes an attachment part 731A to be detachably attached to theelectronic pen main body part 3, an engagement part 732, and a front-endextension part 733A extending from the front-end face 732 a of theengagement part 732 in the opposite direction from the attachment part731A. The attachment part 731A and the front-end extension part 733A ofthe back-end member 73A are both cylindrically shaped and disposed onboth sides of the engagement part 732. The engagement part 732, shapedas a circular plate with a predetermined thickness, separates theattachment part 731A and the front-end extension part 733A from eachother. The attachment part 731A of the back-end member 73A has fittingprotrusions 731 c and 731 b as depicted in FIG. 4D. The fittingprotrusion 731 c is shaped differently from the fitting protrusion 731 aof the attachment part 731 of the back-end member 73 depicted in FIGS.3A to 3F.

Meanwhile, the front-end extension part 733A as depicted in FIG. 4D hasa simple cylindrical shape with no protrusions thereon, differently fromthe front-end extension part 733 of the back-end member 73 of thecentral rod 7 in FIG. 3D. In this example also, the front-end extensionpart 733A of the back-end member 73A has the diameter R1 as depicted inFIG. 4D. As illustrated in the cross-sectional view of the central rod7A in FIG. 4E, the back-end member 73A is attached to the connectionmember 72A when press-inserted into the back-end hole part BH of theconnection member 72A, from the front-end side of the front-endextension part 733A, through the opening on the right end side of theconnection member 72A. In this case, the front-end face of theengagement part 732 of the back-end member 73A and the back-end face(right end face) of the connection member 72A are butted against eachother. This prevents the back-end member 73A from further entering intothe connection member 72A.

Further, the ring-shaped protruding parts 723 c and 723 d formed on theinner wall surface of the connection member 72A function as a back-endholding part that holds down the side surface of the front-end extensionpart 733A of the back-end member 73A. The back-end member 73A can thusbe attached to the connection member 72A with a constant level ofholding strength. In this case, as can be seen in FIG. 4E, thering-shaped protruding parts 723 c and 723 d of the connection member72A toward the side of the back-end member 73A are wider in thelongitudinal direction than the ring-shaped protruding parts 721 c and721 d of the connection member 72A toward the side of the front-endmember 71. Consequently, the connection member 72A can hold the back-endmember 73A with higher holding strength than the front-end member 71. Inthis example as well, the front-end face of the engagement part 732 isbutted against the back-end face of the connection member 72A. Thisprevents the back-end member 73A from further entering into theconnection member 72A.

Meanwhile, the attachment part 731A of the back-end member 73A is fittedto a fitting recessed part 36 c of a pressure transmission member 36Ainside the electronic pen main body part 3. The attachment part 731A hasfitting protrusions 731 c and 731 b formed thereon. The fitting recessedpart 36 c of the pressure transmission member 36A in this example has anengagement part 36 cx that engages with the fitting protrusion 731 c ofthe attachment part 731A of the back-end member 73A as depicted in FIG.4F, differently from the fitting recessed part 36 a of the pressuretransmission member 36 explained above with reference to FIGS. 3A to 3F.

That is, as depicted in the cross-sectional view of the back-end member73A and the pressure transmission member 36A in FIG. 4F, the attachmentpart 731A excluding the fitting protrusions 731 a and 731 b has thediameter R3, which is the same as that of the fitting recessed part 36 cof the pressure transmission member 36A. Thus, the attachment part 731Aof the back-end member 73A has its front end press-inserted and fittedinto the fitting recessed part 36 c of the pressure transmission member36A.

In this example, the fitting protrusion 731 c of the attachment part731A of the back-end member 73A is engaged with the engagement part 36cx of the fitting recessed part 36 c of the pressure transmission member36A. The engagement causes the fitting protrusion 731 b of theattachment part 731A to come into strong contact with the inner wallsurface of the fitting recessed part 36 c. The contact allows thepressure transmission member 36A to hold the attachment part 731A with apredetermined level of holding strength. This in turn allows the centralrod 7A to be attached to the pressure transmission member 36A with apredetermined level of holding strength.

In this example as well, in the connecting portion between theconnection member 72A and the front-end extension part 733A of theback-end member 73A, the ring-shaped protruding parts 723 c and 723 d ofthe connection member 72A strongly hold down the circumference of thefront-end extension part 733A. This ensures hard-to-detach connectionbetween the connection member 72A and the back-end member 73A. In theconnecting portion between the attachment part 731A of the back-endmember 73A and the pressure transmission member 36A, the fittingprotrusion 731 c and the engagement part 36 cx are fitted to each other,with a wide area of contact made between the fitting protrusion 731 band the inner wall surface of the fitting recessed part 36 c of thepressure transmission member 36A to ensure the hold. Whereas theconnecting portion between the connection member 72A and the back-endextension part 712 of the front-end member 71 provides a relativelysmall area of contact between the ring-shaped protruding parts 721 c and721 d on the inner wall surface of the connection member 72A and theback-end extension part 712, the components are held in place with apredetermined level of holding strength.

As described above, the holding strength signifies a strength (force)high enough for members to maintain their connected state by means offrictional force of the connecting portion between the members, or byuse of engaging force of (force to engage with) through-holes orrecesses and projections formed over the connecting portion between themembers. In this example as well, it is assumed that the value A standsfor the holding strength of the connecting portion between theconnection member 72A and the front-end extension part 733A of theback-end member 73A, that the value B denotes the holding strength ofthe connecting portion between the attachment part 731A of the back-endmember 73A and the pressure transmission member 36A, and that the valueC represents the holding strength of the connecting portion between theconnection member 72A and the back-end extension part 712 of thefront-end member 71.

In a case where the central rod 7A depicted in FIGS. 4A to 4F isadopted, the relations between these types of holding strength are alsoA>B>C. That is, the connecting portion between the connection member 72Aand the front-end extension part 733A of the back-end member 73A has thehighest holding strength; the connecting portion between the attachmentpart 731A of the back-end member 73A and the pressure transmissionmember 36A has the second-highest holding strength; and the connectingportion between the connection member 72A and the back-end extensionpart 712 of the front-end member 71 has the third-highest holdingstrength.

Thus, when the central rod 7A is thus attached to the electronic penmain body part 3, the central rod 7A can be pulled by a user pinchingthe pen tip part 711 of the front-end member 71 with nails to pull thecentral rod 7A with a force that is lower than the holding strength Bbut greater than the holding strength C. In this case, while theattachment part 731A of the back-end member 73A of the central rod 7Aremains attached to the pressure transmission member 36A, the front-endmember 71 can be extracted (separated) from the connection member 72A.That is, with the central rod 7A attached to the electronic pen mainbody part 3, the front-end member 71 alone can be replaced. Because theback-end extension part 712 of the front-end member 71 is relativelylong, the front-end member 71 can be extracted from the connectionmember 72A, for example, by repeatedly pulling the central rod 7A, eachtime for a short period of time with a force that is greater than theholding strength C.

Likewise, suppose that the central rod 7A of this example is attached tothe electronic pen main body part 3. In this case, the user may pinchthe pen tip part 711 of the front-end member 71 with nails, for example,to pull the central rod 7A with a force smaller than the holdingstrength A and higher than the holding strength B. This allows thecentral rod 7A as a whole to be extracted from the electronic pen mainbody part 3. That is, the entire central rod 7A attached to theelectronic pen main body part 3 can be replaced.

The strength of the central rod 7A can further be increased when eitheror both of the back-end extension part 712 of the front-end member 71and the front-end extension part 733A of the back-end member 73A iselongated to make the void space 74 in FIG. 4E as narrow as possible.

Advantageous Effects of the Embodiment

The central rod 7 or 7A of this embodiment is made as a high-strengthcentral rod, using the stainless connection member 72 or 72A. Thecentral rod is securely attached to the connection member 72 bypress-inserting the front-end member 71 and the back-end member 73 intothe connection member 72, or is firmly attached to the connection member72A by press-inserting the front-end member 71 and the back-end member73A into the connection member 72A. The attachment can thus withstandrough usages such as writing for a long period of time or writing withhigh writing pressure.

Neither of the front-end member 71 or the back-end member 73 is adheredto the connection member 72, and neither of the front-end member 71 orthe back-end member 73A is adhered to the connection member 72A. Thissimplifies the manufacturing process, and provides the central rod 7 or7A for which the front-end member 71 serving as the pen tip can beeasily replaced.

In the case of the central rod 7, the holding strength is the highestfor the connecting portion between the connection member 72 and theback-end member 73, the second-highest for the connecting portionbetween the back-end member 73 and the pressure transmission member 36,and the third-highest for the connecting portion between the connectionmember 72 and the front-end member 71. Likewise, in the case of thecentral rod 7A, the holding strength is the highest for the connectingportion between the connection member 72A and the back-end member 73A,the second-highest for the connecting portion between the back-endmember 73A and the pressure transmission member 36A, and thethird-highest for the connecting portion between the connection member72A and the front-end member 71. Thus, with the central rod 7 or 7Aattached to the electronic pen main body part 3 via the pressuretransmission member 36 or 36A, only the front-end member 71 held by theconnection member 72 or 72A can be pulled out for replacement.

It is therefore possible to replace the front-end member 71 withoutextracting the central rod 7 or 7A from the pressure transmission member36 or 36A for every replacement. The replacement in this fashionprevents the fitting recessed part 36 a or 36 c of the pressuretransmission member 36 or 36A from being subjected to heavy load (wearand tear). This makes it possible to achieve a central rod having a highaffinity with the electronic pen main body part 3, to which the centralrod 7 or 7A can be detachably attached via the pressure transmissionmember 36 or 36A.

Alternative Examples

In the case of the central rod 7 explained above with reference to FIGS.3A to 3F, the ring-shaped protruding parts 721 c and 721 d are formed onthe inner wall surface of the connection member 72 toward the side ofthe front-end member 71. The ring-shaped protruding parts 721 c and 721d can have an appropriate width large enough to ensure necessary holdingstrength. Whereas two ring-shaped protruding parts 721 c and 721 d areprovided, there may be a single ring-shaped protruding part or three ormore ring-shaped protruding parts, as long as these parts ensurenecessary holding strength. That is, the width and the number ofring-shaped protruding parts to be formed on the inner wall surface ofthe connection member 72 on the front-end member side may be varied suchthat these parts ensure necessary holding strength. Likewise, in thecase of the central rod 7A explained above with reference to FIGS. 4A to4F, the ring-shaped protruding parts formed on the inner wall surface ofthe connection member 72A (i.e., ring-shaped protruding parts 721 c, 721d, 723 c, and 723 d in FIG. 4E) can be varied in width and number aslong as these parts provide necessary holding strength.

The protruding parts formed on the inner wall surface of the connectionmember 72 or 72A are not limited to the ring-shaped type. FIG. 5 is adiagram explaining an alternative example of the central rod 7 or 7A.FIG. 5 depicts a connection member 72B, which is cut in half along itslongitudinal direction with its frontal half removed. As depicted inFIG. 5 , protruding parts of suitable shapes and sizes may be formed onthe inner wall surface of the connection member 72B in place of thering-shaped protruding parts 721 c, 721 d, 723 c, and 723 d. That is,the protruding parts may be provided in diverse shapes, sizes, andlocations. In such cases, there is no need to change the configurationof the front-end member 71 and back-end member 73A.

Recessed parts can be formed on the side surface of the front-end member71 and back-end member 73A in a manner corresponding to the protrudingparts provided on the inner wall surface of the connection member 72 or72A such that the protruding parts and the recessed parts are fitted toeach other. This technique may be effective when the front-end member 71and the back-end member 73A each has a diameter large enough so as tomaintain its structural strength. In other words, the members thatconstitute the central rod 7 or 7A can be adjusted in diameter andlength according to the size of the electronic pen main body part forwhich these members are used.

In the case of the central rod 7 explained above with reference to FIGS.3A to 3F, the through-holes 722 a, 722 b, 722 c, and 722 d are formed onthe side surface of the connection member 72 toward the side of theback-end member 73 in a direction intersecting with the axial centerdirection. In correspondence to these through-holes, the protrudingparts 733 a, 733 b, 733 c, and 733 d are formed on the front-endextension part 733 of the back-end member 73. However, the presentdisclosure is not limited to these specific examples. Alternatively,through-holes of suitable sizes and numbers can be formed in appropriatelocations on the connection member 72 toward the side of the back-endmember 73. In correspondence to these through-holes on the connectionmember 72 toward the side of the back-end member 73, there may beprovided fitting protrusions of the corresponding sizes and numbers onthe front-end extension part 733 of the back-end number 73.

With the central rod 7 depicted in FIGS. 3A to 3F, the ring-shapedprotruding parts 721 c and 721 d are formed on the connection member 72toward the side of the front-end member 71. With the central rod 7Adepicted in FIGS. 4A to 4F, the ring-shaped protruding parts 723 c and723 d are provided on the connection member 72A toward the side of theback-end member 73A. However, the present disclosure is not limited tothese specific examples. Alternatively, these members on which theprotruding parts are formed may be reversed in position. FIGS. 6A to 6Care diagrams each explaining another alternative example of the centralrod 7 or 7A. As depicted in FIG. 6A, a connection member 72C is assumedto be a cylindrical (pipe-like) member with no protruding parts on itsinner wall surface.

In contrast, ring-shaped protruding parts 712 a and 712 b are formed ona back-end extension part 712A of the front-end member 71 as depicted inFIG. 6B. Ring-shaped protruding parts 733 e and 733 f are formed on afront-end extension part 733B of a back-end member 73B as illustrated inFIG. 6C. Given these protruding parts, when the front-end member 71A andthe back-end member 73B are press-inserted into the connection member72C, the connection member 72C holds the front-end member 71A and theback-end member 73B with a predetermined level of holding strength.

In this case as well, there can be provided ring-shaped protruding partsof suitable sizes and numbers on the front-end member 71A and back-endmember 73B in order to attain a predetermined level of holding strength.Furthermore, the ring-shaped protruding parts are not limited to beformed on the front-end member 71A and the back-end member 73B. In amanner similar to the case explained above with reference to FIG. 5 ,there can also be provided protruding parts of desired shapes, sizes,and numbers on the side surface of the back-end extension part 712A ofthe front-end member 71A and on the side surface of the front-endextension part 733B of the back-end member 73B. In the case of thealternative example depicted in FIGS. 6A to 6C, there may be providedrecessed parts on the inner wall surface of the connection member 72C ina manner corresponding to the protruding parts formed on the sidesurface of the back-end extension part 712A of the front-end member 71Aand on the side surface of the front-end extension part 733B of theback-end member 73B.

Also, the relations between the back-end member and the pressuretransmission part in the cases depicted in FIGS. 3A to 3F and 4A to 4Fcan be reversed. FIG. 7 is a diagram explaining another alternativeexample of the central rod 7 or 7A. In the case of this example, anattachment part 731B of a back-end member 73C is configured not to haveprotrusions (protruding parts) or grooves (recessed parts) formedthereon. In contrast, a ring-shaped protruding part 36 dx is formed onthe inner wall surface of a fitting recessed part 36 d of the pressuretransmission member 36. This enables the back-end member 73C to beattached to a pressure transmission member 36B with a predeterminedlevel of holding strength. The width and height of the ring-shapedprotruding part 36 dx can be varied in a manner so as to achieve thedesired level of holding strength.

It is not always necessary to detachably attach the connection member tothe back-end member, e.g., the connection member 72 to the back-endmember 73, the connection member 72A to the back-end member 73A, or theconnection member 72 to the back-end member 73B. FIG. 8 is a diagramexplaining another alternative example of the connection member. Aconnection member 72D depicted in FIG. 8 has the connection member andthe back-end member that are integrally formed. As depicted in FIG. 8 ,the connection member 72D is made of a front-end pipe part 72FT and aback-end attachment part 72BK integrally formed. In this case, theback-end attachment part 72BK performs the function of the back-endmember 73 or 73A in the above-described embodiment.

The front-end member 71 explained above with reference to FIGS. 3A to 3Fand 4A to 4F can be attached to the connection member 72D. The front-endside of the connection member 72D may be configured to have suchprotrusions as those depicted in FIG. 5 . It is also possible toconfigure the front-end pipe part 72FT of the connection member 72D tohave neither protrusions nor recessed parts on the inner wall surface,as explained above with reference to FIG. 6A. In this case, thefront-end member 71A depicted in FIG. 6B is to be attached. Also, theback-end attachment part 72BK can be configured as depicted in FIGS. 4Ato 4F or in FIG. 7 .

In the above-described embodiments, the central rod 7 or 7A isconfigured to apply pressure to the writing pressure detection part 6via the pressure transmission member 36 or 36A. However, the presentdisclosure is not limited to these specific examples. In a case wherethe writing pressure detection part 6 is configured to have a mechanismto hold a central rod, the central rod 7 or 7A may be attached directlyto the writing pressure detection part 6 such that the attachment part731 or 731A may serve as a member (i.e., a pressing element) for pushingthe writing pressure detection part 6.

Application to the Electronic Pen Operating Based on the CapacitanceMethod

The above embodiments have been explained in connection with examples ofthe electronic pen operating based on the electromagnetic inductionmethod. Alternatively, the electronic pen central rod of this disclosurecan also be applied to an electronic pen operating based on thecapacitance method. In this case, the front-end member, the connectionmember, and the back-end member are all configured to be electricallyconductive, so that the central rod as a whole may become electricallyconductive. The electrical conductivity is achieved by using metal orresin mixed with metal powder as the raw materials for forming variousmembers.

It is to be understood that while the invention has been described inconjunction with specific embodiments with reference to the accompanyingdrawings, it is evident that many alternatives, modifications, andvariations will become apparent to those skilled in the art in light ofthe foregoing description. Accordingly, it is intended that the presentinvention embrace all such alternatives, modifications, and variationsas fall within the spirit and scope of the appended claims.

The invention claimed is:
 1. An electronic pen central rod, comprising:a connection member having a front end and a back end; a front-endmember having a pen tip part and a back-end extension part that extendsin an opposite direction from the pen tip part to be detachably held bythe front end of the connection member with a first level of holdingstrength; and a back-end member having an attachment part to be attachedto an electronic pen interior and a front-end extension part thatextends in an opposite direction from the attachment part to be held bythe back end of the connection member with a second level of holdingstrength; wherein the second level of holding strength is higher thanthe first level of holding strength.
 2. The electronic pen central rodaccording to claim 1, wherein the front end of the connection memberincludes a front-end hole in which the back-end extension part of thefront-end member is detachably inserted.
 3. The electronic pen centralrod according to claim 2, wherein a protrusion formed on an inner wallsurface of the front-end hole is used to detachably hold the back-endextension part in the front-end hole.
 4. The electronic pen central rodaccording to claim 2, wherein a protrusion formed on a side surface ofthe back-end extension part of the front-end member is used todetachably hold the back-end extension part in the front-end hole. 5.The electronic pen central rod according to claim 1, wherein the backend of the connection member includes a back-end hole in which thefront-end extension part of the back-end member is inserted.
 6. Theelectronic pen central rod according to claim 5, wherein a protrusionformed on an inner wall surface of the back-end hole is used to hold thefront-end extension part in the back-end hole.
 7. The electronic pencentral rod according to claim 5, wherein a protrusion formed on a sidesurface of the front-end extension part of the back-end member is usedto hold the front-end extension part in the back-end hole.
 8. Theelectronic pen central rod according to claim 1, wherein the secondlevel of holding strength between the back end of the connection memberand the front-end extension part is highest, a third level of holdingstrength between the attachment part of the back-end member and theelectronic pen interior is second-highest, and the first level ofholding strength between the front end of the connection member and theback-end extension part is third-highest.
 9. The electronic pen centralrod according to claim 1, wherein the connection member is formed by ametal material.
 10. The electronic pen central rod according to claim 1,wherein the front-end member is formed by a resin material.
 11. Theelectronic pen central rod according to claim 1, wherein the front-endmember is formed by a felt material.
 12. The electronic pen central rodaccording to claim 1, wherein the back-end member is formed by a resinmaterial.
 13. An electronic pen central rod, comprising: a connectionmember having a front end and a back end; and a front-end member havinga pen tip part and a back-end extension part that extends in an oppositedirection from the pen tip part to be detachably held by the front endof the connection member with a first level of holding strength; whereinthe back end of the connection member is configured to be attached to anelectronic pen interior.
 14. The electronic pen central rod according toclaim 13, wherein the front end of the connection member includes afront-end hole in which the back-end extension part of the front-endmember is detachably inserted.
 15. The electronic pen central rodaccording to claim 14, wherein a protrusion formed on an inner wallsurface of the front-end hole is used to detachably hold the back-endextension part in the front-end hole.
 16. The electronic pen central rodaccording to claim 14, wherein at least one ring-shaped protrusionformed on an inner wall surface of the front-end hole is used todetachably hold the back-end extension part in the front-end hole. 17.The electronic pen central rod according to claim 14, wherein aprotrusion formed on a side surface of the back-end extension part ofthe front-end member is used to detachably hold the back-end extensionpart in the front-end hole.
 18. The electronic pen central rod accordingto claim 13, wherein a second level of holding strength between the backend of the connection member and the electronic pen interior is higherthan the first level of holding strength between the front end of theconnection member and the back-end extension part.
 19. The electronicpen central rod according to claim 13, wherein the front-end member isformed by a resin material and/or a felt material.
 20. An electronic penmain body part, comprising: a housing; and a central rod axiallyextending through the housing, wherein the central rod includes aconnection member having a front end and a back end; a front-end memberhaving a pen tip part and a back-end extension part that extends in anopposite direction from the pen tip part to be detachably held by thefront end of the connection member with a first level of holdingstrength; and a back-end member having an attachment part to be attachedto an electronic pen interior and a front-end extension part thatextends in an opposite direction from the attachment part to be held bythe back end of the connection member with a second level of holdingstrength; wherein the second level of holding strength is higher thanthe first level of holding strength.